"Shut yourself up with some friend in the main cabin below deck on some large ship, and have with you there some flies, butterflies, and other small flying animals. Have a large bowl of water with some fish in it; hang up a bottle that empties drop by drop into a wide vessel beneath it. With the ship standing still, observe carefully how the little animals fly with equal speed to all sides of the cabin. The fish swim indifferently in all directions; the drops fall into the vessel beneath; and, in throwing something to your friend, you need to throw it no more strongly in one direction than another, the distances being equal; jumping with your feet together, you pass equal spaces in every direction."
Those may sound like whimsical instructions to an amateur Noah with a mild interest in sport, but those interested in the history of science will know they introduce one of Galileo's most important hypotheses. In a modern world where the jargon-cluttered intricacies of advanced physics or microbiology seem increasingly to widen the distance between the artistic and the scientific mind, it is easy to be struck by the accessible poetry in the way Galileo set out his ideas on relativity. The image comes from his Dialogues Concerning the Two Chief World Systems and illustrates why, even though the Earth rotates constantly, we do not perceive its motion. The ship becomes a metaphor for the Earth, for when it sets sail, there is no effect at all on the speed at which the butterflies must fly, the fish must swim or the object must be thrown - just in the same way that we can walk, amble or remain rooted in our armchairs while our planet spins at approximately 1,040 miles an hour.
That sense of Galileo's poetry played a big part in the American director Mary Zimmerman's approach to adapting his life story as a libretto for Philip Glass's latest opera. Zimmerman is not well known in England, but her status as the directorial darling of Chicago and New York has been built up by adaptations of Leonardo da Vinci's Notebooks, The Arabian Nights, the Odyssey and, most recently, Ovid's Metamorphoses. In his New York East Village studios, Glass smilingly admits that one of the reasons he chose to work with Zimmerman is: "`Accessibility' isn't a bad word for her. Many people I've worked with - such as Robert Wilson or JoAnne Akalaitis [his first wife] - were very experimental, and there was a much tougher, hard-edged line to those productions."
Fans and detractors alike would agree that "accessibility" is a quality that has rarely graced Glass's enthralling but infuriating collaborations. Einstein on the Beach, the first, longest, most famous and possibly most difficult of his 18 operas, explored the beginnings of atomic energy and tested audiences by exploding the operatic form into a four-and-a-half- hour work, whose then-unique Eastern-influenced notions of rhythm blended with the avant-garde director Robert Wilson's arrestingly symbolic visual style. Galileo Galilei is far slighter, at one and a half hours, and has a distinct narrative, unlike Einstein's image-fuelled progress. Indeed, Zimmerman, whose trademark is to improvise a script through rehearsals, relates that Glass wouldn't write a note before she produced the whole, carefully structured libretto.
The director explains that both she and Glass decided that scientific imagery rather than the political aspects of Galileo's life was going to dominate their work. "I think that Galileo has mistakenly been made an icon of rationality because of his conflict with the church," she declares. …